This invention relates to wireless communication systems, and more particularly to cellular carrier selection within wireless communication systems.
The use of wireless communication systems is growing with users now numbering well into the millions. One of the popular wireless communications systems is the cellular telephone, having a mobile station (or handset) and a base station. Cellular telephones allow a user to talk over the telephone without having to remain in a fixed location. This allows users to, for example, move freely about the community while talking on the phone.
Cellular telephones may operate under a variety of standards including the code division multiple access (CDMA) cellular telephone communication system as described in TIA/EIA, IS-95, Mobile station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System, published July 1993. CDMA is a technique for spread-spectrum multiple-access digital communications that creates channels through the use of unique code sequences. In CDMA systems, signals can be and are received in the presence of high levels of interference. The practical limit of signal reception depends on the channel conditions, but CDMA reception in the system described in the aforementioned IS-95 Standard can take place in the presence of interference that is 18 dB larger than the signal for a static channel. Typically, the system operates with a lower level of interference and dynamic channel conditions.
A cellular telephone communication system typically provides services to an area by dividing the area into many smaller geographic areas, known as cells, each of which is serviced by a transmitter-receiver station, known as a cell site. The cell sites are connected through landlines, or other communication links, to so-called mobile telephone switching offices (MTSO""s) which are, in turn, connected to the public switched telephone network (PSTN). According to current FCC rules, any given area is serviced by up to two competing providers of cellular airtime communication services (i.e., cellular carriers). The two service providers in any given geographic area, commonly referred to as xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d carriers, are assigned different groups of frequencies, or frequency sets, through which services are provided along paging, control, access, and voice channels, as would be understood by those reasonably skilled in the industry and as dictated by technical standards of appropriate regulatory agencies.
When a mobile station first activates in a particular area, the mobile station searches for available service systems. Based on the service subscription and other factors, the mobile station has a preference when selecting a service system. The mobile station generally looks for a system supported by the subscriber, and if none if available the mobile system searches for a compatible system. At present, the mobile station simply searches for systems regardless of the geographic location of the mobile station. What is desired is a system where the mobile station can limit the number of systems required for searching based on the geographic position of the mobile station.
The present invention enhances service system selection by a mobile unit in a wireless communication system. The mobile unit determines its geographic position, and based on that position selects the proper service system. The geographic position may be determined using a global position system, deck reckoning, or estimated from a last known position. The distance of varying service systems from the mobile station can then be calculated and a service system selected based on this distance. The mobile station may also use the position information in combination with a database including position information of service systems to select the proper service system. The position information of the service systems can be included in the system selection database. The mobile station may also map service systems based on position information and service availability. The mobile station can then subsequently refer to these maps to estimate available service.
One aspect of the invention is a method of prioritizing a plurality of service systems in a wireless communication system. The method comprises determining a reference location and calculating a distance from the reference location to each of the plurality of service systems. The method the prioritizes the plurality of service systems based on the distance from the reference location. The reference location may be determined using a global positioning system or dead reckoning, among other techniques. The calculating step further comprises determining a drift term and adjusting the reference location based on the drift term.
Another aspect of the invention is a method of prioritizing a plurality of service systems in a wireless communication system. The method comprises determining a reference location and obtaining a prioritized list of service systems based on the reference location. The reference location may be determined using a global positioning system or dead reckoning. The prioritized list of service systems based on the reference location is obtained from stored data within a mobile station. The data may be stored in the system selection database. The system selection database includes a position reference for each of the plurality of service systems.
Another aspect of the invention is a mobile station for use in a wireless communication system. The mobile station comprises a position determination device and a database of system providers based on position information. The position determination device may be a global positioning system. The database is included in the system selection database, and the selects one of the system providers based on the database information.
Another aspect of the invention is a mobile station for use in a wireless communication system. The mobile station comprises a position determination device and a service detector. The service detector determines if service is available at any given position. The mobile station includes memory locations for storing data regarding service availability for a plurality of locations. A grouping of the memory locations provides a map of a service area showing service availability. The grouping of memory locations containing position information can be converted to a formula defining a service area. Each memory location stores both a latitude and a longitude of a position along with information indicating whether service was available at the position.
Another aspect of the invention is a method of mapping a service system for a wireless communication system. The method comprises establishing a reference location and determining service availability for the reference location. Information on service availability for the reference location is then stored. The method further comprises collecting data on service information for a plurality of reference locations and combining the data to provide a map of a service area showing service availability. The combined data may be converted into a formula defining a service area.